The purpose of this experimental program is to ascertain some of the neurological mechanisms underlying apraxia. The first part of this project will examine apraxic patients with anterior and posterior lesions to determine if they have a receptive deficit such as being unable to comprehend gestures, discriminate between normal and abnormal movements and detect their own errors. The second part of this program will attempt to determine what effect aphasia and apraxia have on acquisition and storage of gestures, retrieval of gestures, gesture span and the ability to retain gestures under distraction conditions. In order to learn if there are interactions between the types of gestures used and the disorders, we will use meaningful (symbolic) and meaningless gestures as well as gestures which are static postures and gestures which use a series of movements.